Inks for conductive materials, the inks containing a dispersion medium (liquid) and a metal powder dispersed in the dispersion medium, and conductive pastes that contain a polymer composition and a metal powder contained in the polymer composition are used for the purpose of, for example, forming conductive patterns of printed circuit boards.
As the metal powder used in such an ink for a conductive material or such a conductive paste, a metal powder containing copper, which is relatively inexpensive and has good electrical conductivity, as a main component is suitably used. However, since a copper powder is relatively easily oxidized, the electrical conductivity may decrease and the particle shape and the particle size may vary in the production.
In view of this, it has been proposed that a small amount of aluminum is contained inside powder particles for a conductive paste, the powder particles containing copper as a main component, to improve oxidation resistance of the powder particles, to prevent electrical conductivity from decreasing, and to stabilize the production of the powder, thereby reducing variations in the particle shape and the particle size (Japanese Unexamined Patent Application Publication No. 2009-235556).